Does behavioral thermal tolerance predict distribution pattern and habitat use in two sympatric Neotropical frogs?

Abstract

Environmental temperatures are a major constraint on ectotherm abundance, influencing their distribution and natural history. Comparing thermal tolerances with environmental temperatures is a simple way to estimate thermal constraints on species distributions. We investigate the potential effects of behavioral thermal tolerance (i. e. Voluntary Thermal Maximum, VT Max) on anuran local (habitat) and regional distribution patterns and associated behavioral responses. We tested for differences in Voluntary Thermal Maximum (VT Max) of two sympatric frog species of the genus Physalaemus in the Cerrado. We mapped the difference between VT Max and maximum daily temperature (VT Max-ET Max) and compared the abundance in open and non-open habitats for both species. Physalaemus nattereri had a significantly higher VT Max than P. cuvieri. For P. nattereri, the model including only period of day was chosen as the best to explain variation in the VT Max while for P. cuvieri, the null model was the best model. At the regional scale, VTMax-ET Max values were significantly different between species, with P. nattereri mostly found in localities with maximum temperatures below its VT Max and P. cuvieri showing the reverse pattern. Regarding habitat use, P. cuvieri was in general more abundant in open than in non-open habitats, whereas P. nattereri was similarly abundant in these habitats. This difference seems to reflect their distribution patterns: P. cuvieri is more abundant in open and warmer habitats and occurs mostly in warmer areas in relation to its VT Max , whereas P. nattereri tends to be abundant in both open and non-open (and cooler) areas and occurs mostly in cooler areas regarding its VT Max. Our study indicates that differences in behavioral thermal tolerance may be important in shaping local and regional distribution patterns. Furthermore, small-scale habitat use might reveal a link between behavioral thermal tolerance and natural history strategies.

Short‐term captivity does not affect immediate voluntary thermal maximum of a neotropical pitviper: Implications for behavioral thermoregulation

“…This small effect size might be due to the small sample size, the small differences in the mean VT Max values of individuals between field‐capture and captivity, a large natural intra‐population variance, or even a combination of these This indicates the need for caution in fully supporting the neglectable effect of time in captivity on the VT Max of B. pauloensis . Although further testing may be necessary before the effect of captivity on thermal tolerance is convincingly understood in pitvipers, we suggest that other interactive factors, such as time of the day when VT Max is measured (Díaz‐Ricaurte et al, 2020) or reproductive status (Ladyman et al, 2003), might play a role. Studies with snake species are usually limited by the difficulty of finding individuals and our study reflects a comprehensive sampling effort over a 2‐year period and thus a reasonably representative sample of this population.…”

“…This differs from other studies on VT Max , where both heating rate and body mass were significant factors for lizards (Camacho & Rusch, 2017), while the VT Max of another neotropical lizard species was significantly affected by time after capture but not by body mass nor acclimation to a constant temperature (Rosso, 2020). For anurans, neither heating rates nor SVL seems to impair VT Max (Díaz‐Ricaurte et al, 2020; Guevara‐Molina et al, 2020). As VT Max has also been shown to be related to life history (e.g., habitat use; Díaz‐Ricaurte et al, 2020), further studies are warranted to investigate how upper thermal limits are constrained by both experimental and ecomorphological aspects across different ectotherm groups.…”

“…For anurans, neither heating rates nor SVL seems to impair VT Max (Díaz‐Ricaurte et al, 2020; Guevara‐Molina et al, 2020). As VT Max has also been shown to be related to life history (e.g., habitat use; Díaz‐Ricaurte et al, 2020), further studies are warranted to investigate how upper thermal limits are constrained by both experimental and ecomorphological aspects across different ectotherm groups. However, this can only be tested by using a standardized and comparable methodology (Pintor et al, 2016).…”

“…Even though VT Max has been documented for lizards (e.g., Brattstrom, 1965; Camacho et al, 2018; Díaz‐Ricaurte & Serrano, 2020; Diele‐Viegas et al, 2018) and recently for frogs (Díaz‐Ricaurte et al, 2020; Guevara‐Molina et al, 2020), the behavioral and physiological thermal tolerance of snakes are understudied (Huang et al, 2007; Lillywhite, 1980; Webb & Shine, 1998). The VT Max is an index measurable under experimental conditions and allows for estimating the behavioral thermal tolerance limits of individuals without exposing them to their physiological critical thermal limits (Camacho & Rusch, 2017; Camacho et al, 2018; Cowles & Bogert, 1944).…”

Linking body condition and thermal physiology in limping crickets: Does limb autotomy incur costs concerning behavioral thermal tolerance?

“…For example, in frogs, it is known that the VT Max is reduced in individuals that are more dehydrated and have a lower body mass (Guevara‐Molina et al, 2020). In addition, the photoperiod can alter the VT Max of the same species (Díaz‐Ricaurte et al, 2020), but in fishes, it is known that, as heating rates increase, CT Max is reduced (Mora & Maya, 2006). This implies that individuals could be exposed to lethal temperatures for longer time periods in case they have too low warming rates (Beitinger et al, 2000; Cocking, 1959).…”